1. Field
This disclosure relates to artillery munitions and particularly to guided artillery projectiles.
2. Description of the Related Art
In this patent the term “artillery projectile” means a projectile configured to be launched from an artillery piece. An “artillery piece”, in turn, means a weapon that launches or fires a projectile by means of the combustion of a propellant charge within a tubular barrel. Artillery pieces include fixed artillery, mobile artillery, guns mounted on vehicles such as tanks, and navel guns, but not, for example, rocket launchers.
The effectiveness of a conventional artillery projectile may be limited by a variety of constraints. Two such constraints are range and accuracy. For instance, an artillery projectile may have a limited range relating to a maximum muzzle velocity for a given combination of projectile, barrel, and propellant. Targets beyond this limited range cannot be effectively reached. Additionally, an artillery projectile may have a fixed trajectory upon firing. As a consequence, an unguided artillery projectile that is not accurately aligned upon firing may miss its intended target. Other factors can reduce the accuracy of the unguided artillery projectile, such as atmospheric conditions, variations in the aerodynamic properties of a given projectile, variations in the artillery piece that fires the projectile, and other factors.
A number of artillery projectile systems have been developed to overcome these limits on conventional artillery projectiles. For instance, rocket assisted artillery-fired artillery projectiles, such as the M549A1 rocket assisted artillery projectile, include an integral rocket motor to increase range. While the propulsion of an integrated rocket motor may increase range, the incorporation of a rocket motor may reduce accuracy.
Highly accurate guided artillery projectiles, such as the Excalibur projectile, have also been developed. Such guided artillery projectiles typically include a guidance system and control surfaces for modifying the trajectory of the projectile. For example, current guided artillery projectiles may include deployable fins, canards, or other control devices that modify the aerodynamic properties of the projectile to affect its trajectory. The guidance system, the deployable control surfaces, and the motors or other actuators for the control surfaces greatly increase the cost and complexity of such a guided artillery projectile. Additionally, the inherent drag of the aerodynamic control surfaces may reduce the range of the projectile.
Throughout this description, elements appearing in figures are assigned three-digit reference designators, where the most significant digit is the figure number where the element first appeared and the two least significant digits are specific to the element. An element that is not described in conjunction with a figure may be presumed to have the same characteristics and function as a previously-described element having the same reference designator.